Slitting machines with scalloped edged blades are used in the smoking products industry for slitting open cartons and packages of cigarettes to recover tobacco rods, which are then fed to ripper machines to reclaim tobacco and tobacco filler for use in other products. A problem involved in slitting cartons to recover tobacco is that, when the slitting blades become dull, the blades shred or rip, rather than cut cleanly, the packaging materials. The shredded paper, paperboard, plastic wrapper, foil and cigarette filter material become mixed in with and contaminate the recovered tobacco filler, creating quality control problems and drastically decreasing the value of the reclaimed tobacco.
The use of well sharpened blades greatly reduces the amount of paper that gets mixed in reclaimed tobacco filler. Maintaining sharp blades in slitting machines proves to be difficult in practice, however. Slitting cigarette cartons and packages is a high wear process and blades dull to unacceptable quality levels quickly, often after cutting only a few hundred cartons. Current practice is to use edge hardened blades until the cutting edges dull, and then replace the blades, a practice which is costly in both maintenance time and blade replacement cost. Furthermore, blade changes are so frequently necessary, as often as several times per hour in high volume operations, that it is not feasible to stop the slitting process to replace the blades each time the edges become dull. Many in the industry simply change blades once or twice each shift, and accept the loss in value for tobacco reclaimed with dull blades.
U.S. Pat. No. 4,829,721 to Wright discloses a honing apparatus for sharpening endless band type blades used in bun slicing machines in the bread industry. The Wright patent apparatus includes a supporting frame holding a pair of fixed elongated hones. The frame is positioned on a bun slicing machine with the hones in proximity with a cutting blade. During the sharpening procedure, the frame is moved so that the hones are positioned at either side of a blade, and the frame is then tilted so that the hones contact both sides of the cutting edge. Sharpening of the blade is effected by the movement of the blade past the hone. The hones also perform two reciprocating strokes in the plane of the blade path during the sharpening procedure.
The Wright apparatus has limitations that make it impractical for use to sharpen blades on a carton slitting machine. Only a small constant area of the hones contacts the blades during a sharpening procedure, and over time the hones are prone to developing flats and loss of abrasive at the contact area. The hones in the Wright patent apparatus must be manually rotated between sharpening operations to expose fresh abrasive to the blades. Because the blades in a carton slitting machine can require sharpening after a few hundred cartons (usually a few minutes), manual adjustments would be labor and time intensive. In addition, carton slitters must cut through plastic and other packaging material which can collect on the blade. During sharpening, this residue can build up on and foul the hones.
Furthermore, it appears that the sharpening operation is done at the relatively slow speed of the moving bun slicing blade. The finish on the blade in this type of honing operation is unacceptable for a carton slitting operation.
The present invention, generally, provides a blade sharpening apparatus for scalloped edged blades in carton slitting machines.
More particularly, the present invention provides a blade sharpening apparatus that can be selectively utilized to sharpen blades in a carton slitting machine without removing the blades from the machine.
The present invention provides a blade sharpening apparatus which hones carton slitting blades to a sharpness required to maintain quality standards that will avoid introducing paper and other unwanted material to tobacco filler reclaimed from slit cartons.
According to a preferred embodiment of the present invention, the rotary hone sharpening apparatus comprises at least two cylindrical hones, each carried on a spindle. The spindles are mounted in bearing sleeves and coupled to a flexible drive shaft for high speed rotation. Flexible drive shafts facilitate the adjustable positioning of the hones relative to the cutting edge of the blade to be sharpened. At least one hone is positionable at each side of a blade cutting edge for sharpening the blade cutting edge. Sharpening is performed on a moving blade, with at least one hone rotating so that a contact surface of the hone is travelling in a direction opposite to the direction of travel of the blade and at least one bore rotating so that a contact surface is moving in the same direction as the direction of travel of the blade. The hone rotating opposite to the blade performs the sharpening operation and the hone rotating in the same direction operates to smooth and deburr the blade edge. According to a presently preferred embodiment, the hones rotate at least 15,000 rpm and more preferably at 20,000 rpm.
In another aspect of the invention, the hones are caused to execute several transverse movements to stroke the blade, exposing more of the hone abrasive to the blade edge to improve sharpening and evenly distribute the wear characteristics of the hones.
According to a further aspect of the invention, the bearing sleeves are each carried in a clamp which is mounted to a pneumatic rotary actuator. The clamps are pivotable for positioning the hones at an appropriate angle to the blade cutting edges. The actuator executes a pivot movement parallel to the plane of the blades causing the hones to move into an engagement location at either side of a blade. The rotary actuator is mounted to a linear actuator for moving the rotary actuator, and consequently the hones, in the direction of the blade width for a sharpening stroking movement.
The present invention provides a blade sharpening device which is installed on a carton slitting machine and can be operated by a machine operator, as needed, to sharpen the slitting blades. Through a circuit of interconnected timing devices, the blade sharpening device of the present invention automatically engages the blade cutting edge and performs a predetermined sharpening operation sequence without operator intervention.
A further aspect of the present invention provides a method for sharpening a scalloped edged blade in a carton slitting machine that includes the steps of reducing the linear speed of the cutting blade, rotating the cylindrical hones, engaging a cutting edge of a blade with the hones, stroking the cutting edge with the hones in a transverse direction several times as the hone rotate, directing air blasts at the hones to remove dust and debris, suctioning off the debris blown by the air blast, and disengaging the hones.